1. Field of the Invention
The present invention relates to curtain wall systems and more particularly relates to a system for improving the heat insulating characteristics of existing curtain wall structures by the conversion and replacement of existing panels having relatively poor heat insulating characteristics with new insulating panels having better heat insulating qualities. Many buildings have been constructed in the past few decades employing curtain wall systems having large glass areas, usually of the single thickness type and supported in a frame work formed of members of extruded aluminum or metal. In the past, the energy cost for heating these types of buildings was relatively low and accordingly, little concern was directed toward the improvement of the heat insulating characteristics of such buildings.
With the recent energy crunch however, resulting in greatly elevated energy costs, improvement of the heat insulating characteristics of existing buildings has become an important factor. In addition to relatively poor thermal characteristics, of many existing buildings, particularly in colder climates, there have been other problems such as the formation of condensation and frost on the interior surfaces of the glass panels and their supporting frame members. Removal of this condensation moisture and the ice or frost creates considerable inconvenience to the occupants and owners of the buildings and sometimes results in physical damage. The aforementioned difficulties and problems do not appear to have been effectively or efficiently corrected with presently available systems on an economically sound basis.
2. Description of the Prior Art
One system for improving the heat insulating characteristics of curtain walls and the like, but without requiring the removal of existing glazing panels is shown and described in U.S. Pat. No. 4,120,127, which patent is assigned to the same assignee as the present application. The references cited against the foregoing patent also disclose several different types of systems for improving the heat insulating characteristics of curtain walls, windows and the like. In actual practice some of these systems have encountered the problems of air leakage through sealing faults and moisture condensation often develops in the space between an existing glazing panel and an additional insulating panel that is added in spaced relation thereto.
Another problem that occurs in systems of this type is that of insuring that an additional glazing panel and the original or existing glazing panel are clean and spotless before a more or less permanent interrelationship between the spaced panels is established. If cleanliness is not achieved, smudges, marks, streaks and the like will then become a more or less permanent part of the completed curtain wall structure which then has an unsightly appearance.